Thermochromic multilayer films of VO2 and TiO2 with enhanced transmittance

Durability of thermochromic VO2 thin films under heating and humidity: Effect of Al oxide top coatings

“…It should be noted that such coatings may be desired not only for oxidation protection but for their optical functionality. Thus the top coating can provide anti-reflection and thereby enhance the luminous transmittance, which is advantageous for windows-related applications [11,16], and studies have been reported for anti-reflecting layers based on oxides of Si [32][33][34][35][36][37], Ti [36][37][38][39][40][41][42], Zr [43] and Al [37]. It is likely that some or all of these oxide layers are able to impart oxidation protection of the underlying VO 2 .…”

Thermochromic undoped and Mg-doped VO2 thin films and nanoparticles: Optical properties and performance limits for energy efficient windows

“…The overarching goal is to assess VO 2 -based materials for energy efficient fenestration, and the present paper is a sequel to earlier ones. [1][2][3][4][5][6][7][8][9][10] Vanadium dioxide is a well known thermochromic material. 11 It undergoes a first-order metal-to-insulator transition, accompanied by a crystal structure transformation from monoclinic (M 1 ) to tetragonal rutile, at a critical temperature τ c ≈ 68 °C.…”

“…[26][27][28][29] Furthermore, antireflection (AR) coatings are able to improve T lum and ΔT sol , and especially good properties have been reported for five-layer coatings of alternating TiO 2 and VO 2 . 2,3 Recent modeling studies on "nanothermochromics" 4,5 have shown that VO 2 nanoparticles can offer significantly higher values of T lum and ΔT sol than films, and these new possibilities have led to a burst of research on such nanoparticles. 6,9,19,22,25,[30][31][32][33][34] 25 This paper is outlined as follows: Section II reports on the samples and treats sputter deposition, compositional and structural data, and optical characterization and properties; this section also contains a discussion of sample quality which-as found in recent work of ours 9 -may be critically dependent on several aspects of the thin film preparation.…”

Nanothermochromics: Calculations for VO2 nanoparticles in dielectric hosts show much improved luminous transmittance and solar energy transmittance modulation

“…Even better properties can be obtained with five-layer coatings of TiO 2 / VO 2 / TiO 2 / VO 2 / TiO 2 . 22,23 Deposition of VO 2 onto ordered arrays of silica microspheres offers other possibilities to increase the transmittance 24 ͑although, apparently, the effect was not reproduced in some other work 25 ͒. Nevertheless the problem with too low transmittance has remained.…”

“…The third problem has to do with the fact that the thermochromic reflectance modulation in VO 2 films is strong only in the near-infrared and at wavelengths for which the solar radiation is weak, which means that the modulation of the solar energy throughput between a low-temperature and a high-temperature state is modest; typically it is ϳ5% for a VO 2 film though, exceptionally, it can run up to 10%-15% in a well designed TiO 2 / VO 2 / TiO 2 / VO 2 / TiO 2 structure. 22,23 VO 2 -based nanoparticles of various types have received much interest in recent work, as discussed at length below, and there are a number of demonstrations that clear-cut thermochromic effects can be observed; data have been obtained for nanostructures made by ion implantation followed by annealing, [27][28][29] ion beam lithography and pulsed laser deposition, 30,31 ultrasonic spray and laser pyrolysis, 32 molten salt synthesis, 33 and aqueous chemistry. 34 Our present study demonstrates that nanoparticles dispersed in a dielectric host have advantages over what a thin solid film can offer.…”